<!DOCTYPE html>
<html class="test-wait">
<body>
<textarea id="target"></textarea>
<!-- crbug.com/ 356194015 -->
<script>
  const target = document.getElementById('target');
  const anim = target.animate({ flexBasis: ['content', 'content'] },
                              { duration: 1000 });
  anim.ready.then(() => {
    document.documentElement.classList.remove('test-wait');
  });
</script>
</body>
